1. Field of the Invention
The present invention relates generally to shock absorbers and, more particularly, to a novel and improved shock absorber which provides a gradual deceleration of a load.
2. Description of the Prior Art
Fluid-flow control apparatuses of the type used as shock absorbers have generally been characterized by complex cylinder and piston assemblies utilizing a considerable number of components to effect absorption or dampening of forces applied to the piston assembly of the shock absorber. Typically, the shock absorbing apparatuses of the prior art include a piston member which is axially movable within a fluid-filled cylinder in response to forces applied to the piston rod. Typical piston arrangements include fixed orifices extending through the piston so that fluid can flow from one side of the piston to the other side as the piston is moved axially within the cylinder. In some conventional shock absorbers, in addition to the fixed passageways through the piston, a spring-loaded plate may be used so that when the fluid pressure on the piston exceeds a predetermined value, the plate will move and open a normally closed relief orifice. Examples of apparatuses of the type aforementioned are described in U.S. Pat. Nos. 3,896,908; 3,731,770; and 3,794,309. In other examples of the prior art such as disclosed in U.S. Pat. Nos. 3,666,256 and 3,605,960, the sleeve member within which the piston is reciprocally mounted is provided with one or more radially disposed orifices which will communicate the fluid within the piston chamber to an accumulator chamber radially displaced therefrom. The aforementioned patents disclose means for varying the size of the orifice through a manually operated and externally mounted mechanism. In all of the aforementioned patents the apparatuses generally include a fixed side passage, either through the piston member or the sleeve member; and while such an orifice may be initially varied (with the exception of the subject matter disclosed in U.S. Pat. No. 3,896,908), the size of the orifice remains constant during movement of the piston. Accordingly, pressure resistant to piston movement within the cylinder is dependent upon the speed of the piston as it advances axially through the cylinder. Since the fluid is allowed to flow through the aforementioned passageways, either in the piston or its sleeve, there will be relatively little resistance to slow the movement of the piston; but as the speed of the piston member is increased, the resistance will increase. An example of a prior art apparatus which employs an adjustable or varied sized orifice to effect the rate of deceleration of the piston is disclosed in U.S. Pat. No. 1,160,976.
While adjustable shock absorbers and the like have been provided heretofore, it should be noted that they are generally costly and complex and, accordingly, do not economically provide for the deceleration action when such operation is required.
3. Prior Art Statement
In the opinion of the applicant, the above-mentioned patents represent the closest prior art of which applicant is aware.